The invention, in some embodiments thereof, relates to the temporary coloring of graying hair, and, more particularly, to agents, formulations, compositions and devices which are useful for temporary shading off local areas of gray or white hair rapidly and simply.
Hair dyes are commonly used to hide the gray and white hairs typically caused by aging, as well as to alter other hair colors to suit personal taste. Hair colorants may be broadly classified into several types, although colorants of different types may be combined, and some colorants may not clearly belong to any one type [Anderson, J. Soc. Dyers Colourists, 116:193-196 (2000); Zviak and Millequant, [Zviak, Charles; Millequant, Jean. Editor(s): Bouillon, Claude; Wilkinson, John. Science of Hair Care (2nd Edition) (2005), 251-275. Publisher: CRC Press LLC, Boca Raton, Fla].
Permanent colorants are usually formed by mixing small aromatic precursors with an oxidizing agent, typically hydrogen peroxide. Following oxidation, the precursors covalently react with each other to form a dye. The small precursor molecules can diffuse into the hair more effectively than the larger dye molecule can diffuse out. An alkalizing agent, typically ammonia, is also added in order to cause swelling of the hairs, which allows maximum penetration of the precursors into the hair. In addition, the peroxide bleaches the original hair color, thereby allowing the color of the dye to completely replace the original hair color. Permanent colorants are quite popular, but they suffer the drawbacks of the complexity of correctly mixing and applying the precursors, and the use of potentially harmful reagents. Thus, permanent colorants are normally applied by professional hair stylists. In addition, even permanent coloring cannot hide the original hair color that inevitably reappears with the new growth of hair.
Demi-permanent colorants are similar to permanent colorants, but use lower concentrations of peroxide, and an alkalizing agent that is less effective than ammonia, but has a less unpleasant odor. Demi-permanent colorants are therefore less effective at penetrating the hair and bleaching the original hair color, and cannot be used to effectively color predominantly gray or white hair. However, the relative gentleness of such colorants makes them desirable when less effective coloring is sufficient, such as when gray or white hairs constitute a minority of hairs.
Semi-permanent colorants typically comprise molecules, such as nitrophenylenediamines and nitroaminophenols, which are small enough to diffuse into the hairs. Such colorants do not require additional reagents and are therefore easy to use, but they are less effective than permanent dyes, fade relatively quickly following several shampooings, and cannot bleach the original hair color.
Temporary colorants typically do not penetrate the hairs, and therefore are capable of only moderate changes in hair color. They are also removed by the first shampooing, and are therefore appropriate for individual occasions, and to make slight alterations to hair color, such as hiding gray or white new growth, until a more permanent colorant is applied. Because temporary colorants need not comprise small molecules capable of penetrating the hair, a wide variety of compounds may be used, which facilitates convenience. For instance, one may select dyes that have no risk of inducing an allergic reaction, which is not possible with more permanent colorants. There is also a large number of shades to choose from.
The ideal characteristics of a temporary hair colorant depend on the exact use of the colorant. Typically, however, it is important that the colorant be easily removable by shampoo, but not by rain, perspiration or friction from clothing or pillowcases. It is also desirable that the colorant have a sufficiently high affinity to hair, and to color hair evenly.
Temporary hair colorants have been used as ingredients in shampoos and conditioners, shading strengtheners, colored hair sprays and mascaras, aimed to be applied to the entire head of hair or as hair streaks. To provide even and stable coloring there are often several families of dyes used within a single formula. The charge of the dyes can be negative or positive to provide low or high affinity to the hair shaft, as dyes with positive charge (basic dyes) have a higher affinity to the hair.
Common temporary hair colorants include azo derivatives, basic triphenylmethane dyes such as methyl violet, azine derivatives such as safranine, and indoamines and indophenols [Zviak and Millequant, supra (2005)]. Colored polymers have been used, as well as artificial melanin.
Polymer colorants with a strong affinity to hair are often semi-permanent or permanent colorants. Examples of polymers with a strong affinity to hair which are semi-permanent colorants are disclosed in U.S. Pat. Nos. 4,182,612, 5,702,712 and 5,827,330.
A polymeric temporary colorant thereafter must have at most a moderate affinity to hair, and more desirable, a low affinity to hair. Examples of polymers suitable for temporary coloring of hair are disclosed, for example in U.S. Pat. Nos. 5,737,907 and 5,891,199.
Tannic acid, or gallic acid produced by hydrolysis of tannic acid, has for centuries been combined with ferrous ions to produce iron gall ink. After writing with the pale ink, the ferrous ions are oxidized by atmospheric oxygen to ferric ions, which react with the tannic acid to produce a dark violet-black organometallic polymer that can permanently bind to proteins, such as those in parchment. Iron gall ink is rarely used today, because paper does not comprise protein, and excess iron atoms are highly corrosive, damaging both paper and pens.
A similar process has been used to permanently or semi-permanently dye hair with a dye that binds the protein of hair. For example, EP Patent No. 327,345 discloses a kit which comprises a shampoo comprising ferrous ion for washing hair, and a solution comprising tannic acid which is applied to the hair after shampooing in order to create a semi-permanent black dye. Such a kit is inadequate for use as a temporary colorant because the colorant is semi-permanent, and because the use of two solutions (a tannic acid solution and a ferrous ion solution) is too lengthy and complex to appeal to consumers. Moreover, the kit disclosed therein must be used more than once in order to achieve full coloration.
Japanese Patent No. 2,014,324 and U.S. Pat. No. 4,946,472 disclose hair colorants comprising ferric ion and tannic acid in a single formulation. The colorants used in the taught formulations, however, are not temporary.
Chinese Patent Application No. 1990-104,017, Japanese Patent Nos. 3,014,160 and 48,031,902 and Japanese Patent Application Nos. 2002-47,287, 1993-312,065, 1988-292,113 and 1984-65,068 disclose permanent or semi-permanent hair colorants comprising ferrous iron and tannic acid in a single formulation. Based on the art of iron-tannic acid colorants, it is believed that ferrous ion undergoes oxidation to ferric ion (e.g. by exposure to air) before reacting with tannic acid to produce a colored polymeric iron tannate. Oxidation of ferrous ions in a hair colorant that has been applied to the hair results in the formation of an iron tannate polymer strongly bound to the hair, making the colorant non-temporary. These patents and patent applications are silent with respect to compositions that comprise tannic acid and ferric iron ions, let alone compositions that are devoid of unbound ferric ions.
Japanese Patent Nos. 61,055,483, 130,823, 94,800 and 93,052 and Japanese Patent Application Nos. 2005-206,160, 2000-85,556, 1990-336,606, 1987-245,287, 1984-177,514 and 1972-81,137 disclose permanent or semi-permanent hair colorants comprising two formulations, one of which comprises iron ions, and the other comprising tannic acid. Mixture of the two solutions in hair allows the production of iron tannates in the hair, the iron tannates thereby becoming bound to the hair.
In addition to the inability of such formulations to serve as temporary colorants, iron-tannic acid hair colorants suffer from several general deficiencies. The dark black color does not appeal to many consumers. In addition, all of the abovementioned formulations comprise unbound iron ions. Unbound iron is corrosive, and ferrous ion in particular produces highly oxidizing free radicals by the Fenton reaction. Excess iron can damage hair and cause unsightly skin hyper-pigmentation [Landsown, Int. J. Cosmetic Sci., 23:129-137 (2001)].
Melanoidins are a family of brownish, colored compounds that result from the interaction between sugars and amino acids under moderate heat. Melanoidins are responsible for much of the browning and flavor of cooked foods, and hence are recognized as highly safe agents. However, melanoidins have not been disclosed as hair colorants heretofore.
It is advantageous for temporary hair colorants to comprise a formulation suitable for applying the colored compound(s) included therein to the hair with the desired ease and convenience. For example, the formulation may include solvents and/or surface active agents which allow the solubilization of the colored compound, and yet are fast drying formulation. It is also desirable in many cases for the formulation to include ingredients that prevent the temporary hair coloring from fading and/or rubbing off prematurely.
PCT Patent Application No. WO 94/10968 teaches an aqueous hair dye composition comprising solubilized melanin and a cationic material which binds the solubilized melanin to the hair via electrostatic interactions. The melanin is preferably solubilized by being oxidized with hydrogen peroxide, which is taught therein as imparting an ionic character to the melanin. The cationic material, such as a quaternium or polyquaternium compound, is taught therein as complexing the anionic melanin in a manner that increases the affinity of the melanin to the hair.
U.S. Pat. No. 6,506,374 teaches a hair coloring composition comprising alcohols to allow quick drying, and a polymer which prevents the color from rubbing off.
U.S. Pat. No. 5,821,240 teaches an aqueous hair coloring composition which includes a quaternary ammonium functional silane to prevent rubbing off.
Japanese Patent Application No. 1993-312,065 teaches a hair coloring composition comprising tannic acid, ferrous salts, and a silicone oil such as a silicone-polyether copolymer. Such silicone oils are non-volatile surface active agents useful in forming smooth films on hair.
As temporary hair colorants are desired for the potential ease and convenience of their use, it is particularly advantageous to have a quick and convenient technique for applying such colorants. Colorants in the form of pencils or wick-type applicators (e.g., U.S. Pat. No. 5,964,222) are frequently used to touch-up the hair along the hair line. Another technique involves combing into the hair a temporary hair colorant gel. In a further technique, hair colorant powder is applied by squeezing a bottle or by an aerosol container to dispense the powder, which is then worked into the hair line with the fingers.
However, none of these techniques is completely satisfactory, particularly when the subject wishes to touch-up the hair line in a quick and convenient manner, without staining or touching the skin.